Anhedonia is a cardinal characteristic of depression which predicts worse treatment outcome and is among the most common residual symptoms following treatment. Behavioral Activation (BA) has been shown to be an effective treatment for depressed adults, and more recently, depressed adolescents. Given its emphasis on systematically and gradually increasing exposure to and engagement with rewarding activities and experiences, BA may be a particularly effective intervention for adolescents experiencing anhedonia and associated reward system dysfunction. In the present study, anhedonic adolescents (AA; n = 39) received 12 weekly sessions of BA and completed a multimodal (i.e., neural, behavioral, and self-report [ecological momentary assessment]) assessment of reward function at pre-treatment and post-treatment (as well as weekly self-report assessments of anhedonia). Typically developing adolescents (TDA; n = 41) completed the same measures at corresponding timepoints. Multilevel models tested pre-treatment reward-related predictors of anhedonia improvement, as well as change in reward measures over the course of BA. Analyses revealed significant reductions in anhedonia following BA treatment. Enhanced pre-treatment neural (striatal) reward responsiveness predicted greater anhedonia improvement. In contrast, baseline self-report and behavioral reward measures did not predict treatment outcome. A group x time interaction revealed greater increases in both reward- and loss-related neural responsiveness among AA relative to TDA adolescents. Consistent with a capitalization (rather than compensatory) model, pre-treatment neural - but not self-report or behavioral - measures of relatively enhanced reward responsiveness predicted better BA outcome. In addition to alleviating anhedonia, successful BA may also increase neural sensitivity to affectively salient (e.g., reward- and loss-related) stimuli among anhedonic youth.